The present invention relates to sand spreaders for applying a snow and/or ice melting mixture of abrasives such as sand and various salts to roadways, and especially relates to motorized, self-propelled sand spreaders.
In Northern climates where safe transportation upon roadways is threatened during periods of ice and/or snow accumulation, it is well-known to use self-propelled sand spreaders to apply a coating of abrasives to the roadway. Such abrasives typically increase friction for motorized traffic passing over the ice and/or snow covered roadway, and simultaneously lower the freezing temperature of the ice or snow in contact with the abrasives. The abrasives usually include a base of sand particles or a similar flowable substance along with various concentrations of salts in either granular or flake-like formations, or occasionally the abrasives will be exclusively a salt or similar chemical. For convenience of description, such abrasives will hereafter be referred to as a sand mixture.
The sand mixture is typically poured by a large bucket loader into a hopper of a "spreader" affixed to a large truck body. Frequently the spreader is mechanically secured within a body of a traditional dump truck, or the spreader may be directly attached to a chassis of the truck. Such spreaders are usually elongate funnel shaped structures of a well-known overall design having a powered conveyer belt at the apex of the funnel, wherein the conveyor belt moves in an endless loop in a direction parallel to an axis of motion of the truck during spreading of the sand mixture. The funnel shaped walls serve to direct the sand mixture onto the conveyor belt, and the conveyor belt moves the sand mixture toward a back end of the spreader into a discharge chute. The chute directs the sand onto a rotating spinner assembly that broadcasts the sand over the roadway behind truck in a well-know manner as the truck moves forward. More modern spreaders frequently include liquid injectors that include placement of a tank on or near the spreader and a powered distribution assembly that injects the liquid onto the roadway with the sand mixture.
Known sand mixture spreaders are therefore complex, including many costly moving parts that necessarily result in an array of problems. For example, the conveyor belt assemblies of known sand spreaders are typically driven by expensive, complex hydraulic motors and pumps, or separate, small internal combustion motors and related multiple bearing and axle assemblies that require constant maintenance where they are exposed to abrasive, high salt concentration environments. The belts are known to bind up and stall if large, rock-sized pieces of the sand-mixture wedge between the belts and outlets to spinner assemblies. Also, know spreaders using conveyor belt assemblies typically include reduction gear boxes an associated chains and sprocket gears. Therefore, great care must be taken to insure that consistent sized-particles of sand are placed in such spreaders.
Additionally, such conveyor belt types of spreaders operate at maximum efficiency through only a narrow range of belt speeds, while the truck carrying the spreader ordinarily operates at a wide range of road speeds, especially where the truck operates in an urban or suburban environment. Consequently, flow rate of sand discharged off of the spinner assembly onto the roadway is typically set by a truck operator prior to application of the sand mixture to the roadway by adjusting mechanical deflectors within the distribution chute between a wide open position to a barely open position, depending upon the intended route of the spreader and the particular snow/ice conditions on the roadway. Therefore, efficient application of the sand mixture and best usage of the time of the operator is compromised because of inherent structural limitations of such common, known spreaders.
A further cost and time constraint of known spreaders is associated with securing such a spreader in a dump truck body or onto a truck chassis. The spreaders are very heavy and are frequently raised onto costly, complex support racks, under which the truck is positioned. The spreaders are then lowered onto the truck and mechanically secured such as by chains, etc. The truck must be further modified by having well-known power take off hydraulic lines or mechanical shafts directed to operating and/or control systems of the spreaders, and by having control apparatus secured within reach of the operator within the truck. As is apparent, when such a spreader is secured to a large dump truck, the truck cannot be used for alternative tasks requiring usage of its dump body until the spreader is removed, requiring further labor and time expenses.
An additional limitation of known spreaders is that they are incapable of mixing abrasives together. For example, granular or flaked salt chemicals must be mixed with a base of sand for even distribution upon the roadway to maximize the capacity of the sand mixture to enhance friction and melting of the snow and/or ice on the roadway. Typically such mixing is performed at a storage site for the sand mixture, and the mixture is then loaded into the spreader. Once mixed, however, the sand mixture must be stored under a roof, because rain water or melting snow could melt the salt chemicals causing them to run out of the mixture thereby depleting the value of the sand mixture and often rendering the melted chemicals an environmental hazard. Consequently, large storage barns must be constructed at such sand mixture loading sites to protect the sand mixture from rain or snow, at great cost and loss of the barn area of the site for alternative usage.
During periods of time that known sand spreaders are utilized to treat roadways, known "transit" or cement mixers are typically idle, because construction activities requiring pouring of cement from cement mixers are usually stopped during snow and/or ice storms. Self-propelled cement mixers of the type having a large powered barrel for rotatably storing, mixing and rear or front discharge of a sand-cement mixture are not known to have been used to distribute a sand mixture to roadways to enhance friction and/or lower the freezing temperature of snow and/or ice on the roadway.
Accordingly, it is a general object of the present invention to provide a cement mixer sand spreader that overcomes the problems of known sand spreaders.
It is a more specific object to provide a cement mixer sand spreader that minimizes modifications to a cement mixer vehicle to permit the vehicle to apply a sand mixture to a snow and/or ice covered roadway.
It is another specific object to provide a cement mixer sand spreader that enables an operator of the cement mixer sand spreader to readily adjust rates of discharge of a sand mixture out of the spreader while the spreader is spreading a sand mixture.
It is yet another object to provide a cement mixer sand spreader that enables mixing of a sand and salt chemical within the spreader while the spreader is operating thereby obviating any pre-mixing of chemicals making up the sand mixture.
These and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.